The middle ear, composed of ossicles and soft tissues including the tympanic membrane, ligaments, and joints plays a vital role in the transmission of sound and the sense of hearing. The mechanical properties of soft tissues change in middle ear diseases such as otitis media. As a consequence, the mobility of ossicular chain is reduced and significant conductive hearing loss occurs in otitis media ears. However, the mechanical property changes in soft tissue associated with disease are largely unstudied. It is almost impossible to identify mechanical changes of middle ear tissues in relation to hearing loss based on current clinical tools. The goal of this project is to characterize the biomechanical behaviors of soft tissues in normal and diseased ears, identify soft tissue changes which are associated with changes in normal hearing, and provide an improved 3-dimensional (3D) ear model to visualize and quantify structure-function relations in various diseases. Otitis media (OM) will be the primary focus for the project. Three specific aims are proposed: Aim 1: To Identify changes of mechanical properties of middle ear soft tissue in OM. We hypothesize that the change of mechanical properties of ear tissues in OM is related to morphological changes of the tissue in response to fluid, pressure, and duration of the OM. This hypothesis will be tested by comparison of measurement results of the ear tissues between normal and diseased ears in chinchillas using dynamic mechanical analyzer, split Hopkinson tension bar, acoustic driving with laser Doppler vibrometry (LDV), fringe Moiri system, and FE modeling of soft tissue. Aim 2: To quantify the effect of biomechanical changes of the middle ear on sound transmission in OM. It is hypothesized that the hearing loss in OM is caused by a combination of changes of ear tissues, fluid, and pressure in the middle ear. This hypothesis will be tested by measuring the ABR thresholds and the changes of middle ear transfer function and sound energy transmission in chinchilla OM ears with a novel theoretical analysis of fluid, pressure, and tissue properties with the aid of FE model of chinchilla ear to describe the mechanism of OM. Aim 3: To continue the development of our 3D FE model of the human ear with clinically-relevant applications. We will incorporate into the model with tissue properties determined in Aims 1 and 2, the microstructures of the TM and ISJ, and the stapedius muscle function. A FE model of pediatric ear will be created for studying OM in young children. The acoustic-mechanical vibration and energy transmission through the middle ear in diseased ears will be visualized and quantified in the 3D FE model by 4 novel model-derived auditory test curves, named as: the middle ear transfer function (METF), energy absorbance (EA), admittance tympanogram (AT), and TM holography, which will assist physicians and audiologists to interpret the diagnostic test results and identify the specific type of middle ear disorders.